DISGRACED former minister Mark McDonald has admitted he might run into the women who accused him of harassment when he returns to the Scottish Parliament today – but insisted he is “morally justified” in staying on as an MSP.

Mr McDonald – who quit the SNP after a string of allegations of sexual misconduct – has been missing from Holyrood for almost four months.

But he denied he is a “sex pest” and said allegations he groped a woman were untrue, while admitting to inappropriate behaviour in the past.

He now faces a fresh probe after a former party colleague lodged an official complaint containing a number of explosive allegations.

READ MORE: MSP makes formal complaint over Mark McDonald’s Holyrood return

SNP deputy leadership hopeful James Dornan accused Mr McDonald of repeatedly harassing one of his staff members.

In a letter to Holyrood’s standards committee, Mr Dornan said this had contributed to the woman becoming so unwell she was hospitalised.

He said it would be a “clear negation of the duty of care that the parliament has to all its members of staff” if Mr McDonald was allowed to return.

The former SNP children’s minister is expected to give a short statement to media when he returns to Holyrood tomorrow.

He has been given a temporary office in Holyrood's basement after he was shunned by his former SNP colleagues, but journalists were yesterday warned off trying to discover its whereabouts by parliament authorities.

Pressure has been mounting on Mr McDonald to resign his seat since he apologised last week.

READ MORE: MSP makes formal complaint over Mark McDonald’s Holyrood return

An internal investigation for the SNP into allegations made by three women identified "persistent" behaviour including inappropriate and unwanted text messages, unwanted attention and exploiting his position of power.

The married father-of-two had already resigned as childcare minister when the allegations first emerged in November.

First Minister and SNP leader Nicola Sturgeon – alongside several MSPs and MPs – has urged him to leave Holyrood.

However Mr McDonald has insisted his return is morally acceptable. He told the BBC: "Morally I can justify it because, as I have said, my approach to this has been to own the mistakes that I have made but to demonstrate that I have learned from them and that I am capable of changing as a result of those.

"I am asking people to afford me that opportunity, and I hope that people will do that.

"I accept that many relationships are going to have to be rebuilt – some people will want nothing to do with me and I have to regretfully accept that, but there are some people who I think will want to offer me that opportunity to demonstrate that I've learned from this and that I've changed."

A Scottish Tory spokesman branded Mr Dornan’s letter “astonishing”, adding: “The allegations are extremely serious and must be fully investigated.”

READ MORE: MSP makes formal complaint over Mark McDonald’s Holyrood return

Scottish Liberal Democrat Leader Willie Rennie said Mr McDonald's position was now untenable.

He said: “I appeal to Mark McDonald’s friends and family to step in and advise him to stand down before he causes the victims any more distress or himself any more damage.”

A Scottish Parliament spokeswoman said: "We can confirm that the convener of the Standards, Procedures and Public Appointments Committee has received a letter from Mr Dornan. It will now be for the committee to decide how its wishes to proceed when it meets on Thursday."